1. Field of the Invention
This invention relates to a graph display control apparatus and a graph display control method which display a plurality of graphs simultaneously.
2. Description of the Related Art
Some of the known electronic calculators, including scientific electronic calculators, are so-called graph function calculators which have the function of displaying a graph corresponding to a mathematical expression input by the user.
When the user inputs a function expression and gives an instruction to draw a graph, the graph function calculator draws and displays a graph on the orthogonal coordinates. Thereafter, the graph function calculator finds characteristic points (or equation solution points), such as a maximum and a minimum of the graph or the intersections of graphs, and displays their positions or values.
Because (1) the screen is small and (2) the resolution of the dot-matrix display is low, the graph function calculator has the problem of being incapable of visualizing the state near the equation solution point accurately.
With such a graph function calculator, the user can enlarge and display a graph by manual operations, but has the following problems: (1) the manual operations are laborious and (2) the enlarged display causes only a part of the graph to be displayed, preventing the entire picture from being comprehended.
To overcome those problems, a graph function calculator has been considered which has the function of enlarging and displaying only a specified range of the graph, while causing the display size of the entire graph to remain unchanged (e.g., refer to Jpn. Pat. Appln, KOKAI Publication No, 2002-259348).
In the case of a graph function calculator with the conventional enlarged display function, the user has to determine whether to enlarge and display the graph and then operate the calculator, making the procedure troublesome, which becomes a problem.